1. Field
One embodiment of the present invention relates to a technique associated with die casing.
2. Description of the Related Art
A cold-chamber die-casting die is provided with a biscuit section, product section, main runner, and main gate. The biscuit section receives a molten metal from an injection apparatus of a casting machine. The product section is a space in which a product is to be cast. The main runner guides the molten metal from the biscuit section toward the product section. The main gate is provided between the main runner and the product section and has a sharply reduced thickness such that the flow (i.e., stream) of the molten metal can be accelerated.
Since the solidification time of the molten metal of, for example, a magnesium alloy is very short, the die-casting die of which the cross-sectional flow area (i.e., cross-sectional area of a space into which the molten metal is to be poured) is small may possibly fail to fill the molten metal into every corner of the product section, thereby causing insufficient filling. Therefore, some die-casting dies that are liable to insufficient filling are provided with sub-runners and sub-gates that laterally support the flow in the product section, in addition to the main runner and the main gate.
A die that is provided with sub-gates around a product section is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-48047. In this die, the sub-gates are arranged beside the product section. A molten metal is poured into the product section directly and also through the sub-gates.
In recent years, there has been a growing demand for die-casting products with further reduced thicknesses, e.g., thicknesses of 0.6 mm or less.
In order to meet the above demand, the inventor hereof is trying to develop dies for thin-wall casting. In this process, the inventor found that air in one such thin-wall casting die was easily left between molten metal introduced through a main gate and molten metal introduced through sub-gates, and that defective casting, involving mold cavities, incomplete filling, or molten metal wrinkles, was liable to occur.
Since the die described in Jpn. Pat. Appln. KOKAI Publication No. 2003-48047 is provided with the sub-gates that surround the product section, air is easily left in the product section, so that it is difficult to reduce defective casting in this die.